The present invention relates generally to power sources for providing alternating current, for example to be used in welding apparatuses. More particularly the invention relates to an inverter or providing alternating current to a load including a welding circuit, a method of controlling an inverter to provide alternating current to a load including a welding circuit, an internal memory comprising software for controlling the steps of a method for controlling an inverter to provide alternating current to a load including a welding circuit and a computer readable medium for controlling a computer to perform the steps of a method for controlling an inverter to provide alternating current to a load including a welding circuit.
The purpose of an inverter is to generate alternating current to a load. For some applications it is important that the current provided to the load has a true sinus wave shape. Other implementations may require that the power dissipation in the load is as constant as possible. In the latter case, it is key that the current direction be reversed as rapidly as possible, i.e. that the current as a function of time has a shape being as close as possible to a square wave. Inverters for welding current sources normally represent implementations where a square-wave shaped current is desirable. Namely, in addition to providing relatively constant power dissipation in the load, this reduces the risk of arc outage in connection with reversing the current.
The patent document EP 1 422 011 discloses a welding-type power supply unit, which includes a so-called snubber circuit. The snubber circuit recovers energy that would otherwise not be used, and thus economizes the energy usage. The snubber circuit also protects various components in the circuitry from harmful voltage spikes. Additionally, freewheeling switches here provide a freewheeling current path for any energy having been stored temporarily in the snubber inductor.
The known snubber-circuit design may be advantageous from an energy-efficiency point-of-view. However, the freewheeling switches render the design complex. Each switch also requires a specific control signal, which require that processing tasks be executed by a control unit.